Plastic bonded explosive composition

ABSTRACT

An explosive composition which will withstand temperature exposure and temperature shock at supersonic speeds and upon environment exposure. It consists essentially of a high explosive pre-coated with a polyester resin consisting of the polyester portion of Laminac 4116 and 4134 admixed with vinyl toluene, alpha-methyl styrene and diallyl phthalate.

United States Ratent Wiebke et a1.

PLASTIC BONDED EXPLOSIVE COMPOSITION Inventors: Ethyl F. Wiebke; CharlesW.

Falter-man, both of China Lake, Calif.

The United States of Amercia as represented by the Secretary of theNavy, Washington, DC.

Filed: May 19, 1967 Appl. No.: 642,651

Assignee:

11.8. C1. 149/19.5; 149/11; 149/19.91; 149/19.93; 149/92; 149/105;260/78.4 UA; 264/3 R Int. Cl. C06B 45/10 Field of Search 149/19, 92, 11,19.91, 149/19.5, 19.93, 105; 264/3, 3 R; 260/291, 260/78.4 UA

Primary Examiner-Leland A. Sebastian Attorney, Agent, or FirmR. S.Sciascia; Roy Miller [57] ABSTRACT An explosive composition which willwithstand temperature exposure and temperature shock at supersonicspeeds and upon environment exposure. It consists essentially of a highexplosive pre-coated with a polyester resin consisting of the polyesterportion of Laminac 4116 and 4134 admixed with vinyl toluene,alpha-methyl styrene and diallyl phthalate.

3 Claims, N0 Drawings PLASTIC BONDED EXPLOSIVE COMPOSKTION The inventionherein described may be manufactured and used by or for the Governmentof the United States of America for governmental purposes without thepayment of any royalties thereon or therefor.

The invention relates to an improved castable plastic bonded explosivecomposition and its preparation capable of withstanding temperatureexposure and temperature shock at supersonic speeds and uponenvironmental exposure.

Castable plastic-bonded explosive formulations developed up to thepresent time have shown energy characteristics similar to those ofComposition B, a British developed composition during the period betweenWorld Wars I and II and which was standardized by the United Statesearly in World War II. Composition B is a TNT-based composition and ithas been considered a desirable and worthwhile goal to attempt toimprove the explosive potential of the plastic-bonded types to exceedthat of the best TNT-based formulations and still retain the desirablephysical properties of the former. The present invention provides aformulation superior to the aforementioned conventional TNT- basedexplosives not only in respect to their resistance to melting at hightemperatures but also in regard to physical properties and ease ofprocessing.

The general purpose of this invention, therefore, is to provide anexplosive composition for a missile warehead which can withstand theenvironment at the supersonic speeds to which the warhead will besubjected.

An object of this invention is to provide an explosive composition whichcan be used in applications involving aerodynamic heating.

Another object of this invention is to provide an explosive compositionwhich has a reduced exotherm, is less brittle than other plastic bondedexplosives, and resists cracking.

Yet another object of this invention is to provide an explosivecomposition which has the economic advantages of savings in time andmaterials used.

Other objects and the attendant advantages of this invention will bereadily appreciated as the same become better understood by reference tothe following detailed description.

The invention contemplates incorporating a polyester resin-coatedexplosive selected from the group consisting ofcyclotrimethylenetrinitramine (RDX), cyclotetramethylenetetranitramine(HMX), diaminotrinitrobenzene (DATB) and others with a bindercomposition consisting essentially of vinyl toluene, alpha-methylstyrene and diallyl phthalate. The explosive is pre-coated with amixture of unsaturated polyester resin sold under the tradename LaminacEPX 147-1 by American Cyanamid Company.

In preparing the formulation the liquids consisting of vinyl toluene,alpha-methyl styrene and diallyl phthalate were added to a mixing kettlethen the resin-coated explosive was added and the mixture stirred untilthe resin dissolved and the explosive dispersed. Vacuum is usuallyapplied to the kettle during the last portion of the mixing operation toremove entrapped air. When thoroughly mixed the batch was catalyzed. Thecatalyst-accelerator combination used consisted of methyl ethyl ketoneperoxide in the form of 60% solution in dimethyl phthalate and cobaltnaphthenate solution (6% cobalt as metal). The amounts ofcatalystaccelerator may be adjusted to produce the desired pot life ofthe composition. Acceptable results have been obtained using 0. 1%cobalt naphthenate solution and 0.5% methyl ethyl ketone peroxidesolution (based on binder weight of the batch).

It is important to use this particular catalyst combination, since theuse of other catalyst systems in particular, t-butyl perbenzoate, willcause the diallyl phthalate to enter into the polymerization reactionrather than acting as a plasticizer and the resulting product will lackflexibility and low shrinkage characteristics. After the catalyst hasbeen mixed in, the material is cast into preforms or molds and allowedto stand at room temperature until gelled and cured. Heat may be appliedto accelerate curing, the temperature being limited by the nature of theexplosive filler.

The explosive composition should have as high an explosive content aspossible, being limited by the practical consideration of processabilityand explosive sensitivity.

The following formulation has a detonation velocity of 8060 m/sec in 1/8 inch-diameter and an impact sensitivity of 36 cm (as compared toComposition Bs 33 cm).

For applications where a lower detonation velocity is acceptable ordesired, the binder content may be increased.

In preparing the binder, diallyl phthalate may range from 20 to 25percent of the binder composition. Above 25% the product is too weak andbelow 20% it is not sufficiently flexible. When omitted from the binder,the solutility characteristics of the binder are altered to the pointwhere phase separation occurs. The vinyl toluene contributes to reducingthe shrinkage of the cross-linked polyester, but produces a vigorousexotherm. In combination with alpha-methyl styrene, the polymerizationis controlled and a negligible exotherm results. The alpha methylstyrene content may vary between 25%, the 2% level being adequatewithout slowing down the reaction excessively.

Small samples of the explosive composition were prepared using 17, 20,25 and 22.5% diallyl phthalate. The sample using 22.5% diallyl phthalatein the binder showed minimum cracking.

The percentage binder is important to the viscosity and processabilityof the composition. A total binder content of 17% produced a betterdetonation velocity than Composition B. Less binder than this would makeit too difficult to process on a large scale and more binder woulddecrease its energetic properties.

Two pound samples of the present formulation and several similarformulations were cured nearly adiabatically and their temperature riseswere recorded. The formulation set out above exhibited an exotherm ofapproximately 5 F. While the other plastic-bonded explosives showed asmuch as 100 F. rise.

The combination of vinyl toluene, alpha-methyl styrene and diallylphthalate as a binder for unsaturated, styrene free polyester resincoated high explosives is new and the composition produced has superiorphysical properties. The diallyl phthalate, a potentially reactivemonomer, acts as a solubilizing agent and plasticer.

The Laminac unsaturated polyester resin EPX 147-1 which is used topre-coat the high explosive before mixing with the liquid binder in theformulations described herein is manufactured by American Cyanamid. Itis a monomer free polyester resin consisting of a blend of the reactionproducts of adipic acid, maleic acid with diethylene glycol and phthalicacid, maleic acid with propylene glycol. The method of preparing thereaction products is fully described in U.S. Pat. No. 2,255,313, issuedSept. 9, 1941, which discloses preparation by reacting an alpha,beta-ethylenically unsaturated dicarboxylic acid and a glycol with orwithout a dicarboxylic acid free of non-benzenoid unsaturation.

The binder consisting essentially of unsaturated polyester resin, vinyltoluene, alpha-methyl styrene and diallyl phthalate is potentiallyuseful for propellants and pyrotechnics formulations.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

What is claimed is:

1. The plastic bonded explosive composition consisting essentially ofIngredients Percent by weight A high explosive Binder said explosivebeing a member selected from the group consisting ofcyclotetramethylenetetranitramine, cyclotrimethylenetrinitramine, anddiaminotrinitrobenzene;

said binder consisting of 42.4% of a blend of the reaction products ofadipic acid, maleic acid with diethylene glycol and phthalic acid,maleic acid with propylene glycol; 33.1% vinyl toluene; 2% alphamethylstyrene; and 22.5% diallyl phthalate.

2. The process for the preparation of the composition of claim 1 whichcomprises a. pre-coating said high explosive with a blend of thereaction products of adipic acid and maleic acid with diethylene glycol,and phthalic acid and maleic acid with propylene glycol;

b. mixing together vinyl toluene, alpha-methyl styrene and diallylphthalate to form a homogeneous liquid binder;

c. stirring said pre-coated explosive into said binder until the resinis dissolved and the explosive is dispersed thereby forming a mixture;

d. catalyzing said mixture with a solution of cobalt naphthenate andmethyl ethyl ketone peroxide;

e. casting said catalyzed mixture into molds; and

f. curing said mixture at room temperature until a solid product forms.

3. A binder formulation consisting essentially of the following:

1. THE PLASTIC BONDED EXPLOSIVE COMPOSITION CONSISTING ESSENTIALLY OF
 2. The process for the preparation of the composition of claim 1 which comprises a. pre-coating said high explosive with a blend of the reaction products of adipic acid and maleic acid with diethylene glycol, and phthalic acid and maleic acid with propylene glycol; b. mixing together vinyl toluene, alpha-methyl styrene and diallyl phthalate to form a homogeneous liquid binder; c. stirring said pre-coated explosive into said binder until the resin is dissolved and the explosive is dispersed thereby forming a mixture; d. catalyzing said mixture with a solution of cobalt naphthenate and methyl ethyl ketone peroxide; e. casting said catalyzed mixture into molds; and f. curing said mixture at room temperature until a solid product forms.
 3. A binder formulation consisting essentially of the following: 